This invention relates to highly absorbent fiber, for example, viscose rayon, hydroxypropylcellulose, and hydroxyethylcellulose, made from wood pulp or other cellulosic materials, which are useful in the production of nonwoven articles such as diapers, tampons, sanitary napkins, medical sponges, soil mulches, wiping cloths, and the like. Each of these applications requires a material having a high capacity for absorbing and retaining water and other aqueous fluids, particularly body fluids. Cellulosic fibers have found wide use in these and similar applications because of the hydrophilic nature of the cellulose molecule and the fibrous structure which contributes integrity, form, shape, wicking ability, and liquid retention to a nonwoven material.
Some examples of attempts to increase the absorbency of rayon fibers can be found in such techniques as U.S. Pat. No. 3,419,345 to Parrish in which rayon fibers are neutralized with a sulfate solution; and, U.S. Pat. No. 3,525,735 to Miller, in which alkali cellulose is reacted with an etherifying agent comprising acrylonitrile. In fact, the incorporation of additive material in viscose to modify the absorbency of the resulting rayon product is known in the art. As examples only, attention is called to U.S. Pat. No. 3,423,167 to Kuzmak et al., 3,847,636 to Smith, and U.S. Pat. No. 3,525,735 to Miller, which teach the incorporation into viscose of carboxymethylcellulose and carboxyethylstarch and acrylonitrile respectively, to increase the hydrophilic properties of the fiber. Typically, for maximum absorbency, the additive is in a salt form in the fiber, as in U.S. Pat. No. 3,844,287 to Smith in which the additive is the alkali metal and ammonium salt of polyacrylic acid.
The instant invention is directed to the incorporation of additive material of a structure not suggested by the prior art. The essential monomer used with this invention is described in detail in U.S. Pat. No. 3,506,707 to Miller et al.